2 Specification

3 Description

F08GEF (DSPTRD) reduces a real symmetric matrix A, held in packed storage, to symmetric tridiagonal form T by an orthogonal similarity transformation: A=QTQT.

The matrix Q is not formed explicitly but is represented as a product of n-1 elementary reflectors (see the F08 Chapter Introduction for details). Routines are provided to work with Q in this representation (see Section 8).